Supplying a clean direct current (DC) power source to electronic devices in an efficient manner has become increasingly important. Power converters are used to take an alternating current (AC) or DC source as an input and generate at its output a clean DC voltage to power electronics connected to the power converter. Conventionally, a power converter receives as an input an AC voltage and converts it to a DC supply voltage to power devices such as laptops, desktop computers, computer servers, mobile phones, televisions, home appliances, battery chargers, or any other electrically powered devices requiring a DC voltage source.
One conventional method for performing such AC to DC power conversion uses linear power supply. Linear power supplies conventionally step down the AC voltage using a transformer, rectify the stepped-down voltage with a rectifier bridge, smooth the rectified voltage with an output capacitor to generate, and regulate the smoothed output voltage with a regulator. Linear power supplies often suffer from low power conversion efficiency from the input AC power to the output DC power. Furthermore, the necessary size of a transformer for systems operating at a line frequency of 50 Hz-60 Hz is too large for portable applications and is often relatively expensive.
A second conventional method for performing AC to DC conversion uses switch-mode power supplies. Switch-mode power supplies typically have a smaller form-factor than comparable linear power supplies. However, switch-mode power supplies have undesirable non-linear characteristics that may introduce harmonics and power factor problems. Furthermore, many switch-mode power supplies may not adapt well to varying operating factors/conditions.
Conventional switch-mode power supplies chop a full sine wave input, harvest the associated energy from the chopped input portion, convert and transfer the energy from the chopped input portion to the DC output stage. The chopping is not dependent on the input waveform, but rather a static, timed chopping procedure. For instance, conventional power supplies may be designed to chop a full sine wave input such that all portions of the waveform are chopped at regular intervals, for instance regularly spaced intervals at a rate of 120,000 times per second, and transferred to the output regardless of the actual behavior and zero-crossing timing of the input waveform. Alternatively, a conventional power supply may be designed to take portions of the input equally sized in energy. In this way, the system is designed to take statically defined, equal in energy portions of the input waveform to produce the DC output. Such systems are designed to take input portions at predefined moments wherein a portion taken from a lower voltage region of the input is wider than a portion taken from a higher voltage region such that the energy harvested from each portion is equal to the energy harvested from the other portions. In the constant width portion example and in the constant energy portion example, portions of an input voltage waveform are always taken in the same way and at the same moments from one period (or half-period) to the next. Furthermore, conventional power converters do not recalibrate based on direct measurements of efficiency. Conventional power converters perform measurements to ensure sufficient power is delivered to the output without direct considerations for efficiency. Conventional power converters may indirectly monitor and control efficiency by, for instance, monitoring and controlling an input current. Also, conventional power converters use rectifiers that are inherently lossy. Conventional converters also do not predict a change in future operation based on current operating factors/conditions and historically demonstrated operating factors/conditions.
There is a need for more efficient power conversion. There is a need to more efficiently harvest and use the input waveform when performing power conversion than is done in conventional converters. There is a need to adjust how power is converted based on operating factors/conditions and to harvest and use portions of the input based on these operating factors/conditions. Furthermore, there is a need to selectively use any portions of the entire input sine wave to optimize operation and maintain operating conditions within acceptable thresholds. There is also a need to operate at high frequencies, which allows for the use of smaller components than those used in conventional linear supplies.